In general, the present invention relates to an image-pickup display apparatus comprising a camera unit and a display unit. More particularly, the present invention relates to an image-pickup display apparatus capable of adjusting a display on a display unit thereof in accordance with the brightness of its circumference.
Such an image-pickup display apparatus can be utilized as an electronic mirror of an automobile or a portable video camera.
With the image-pickup display apparatus used as an electronic mirror, for example, the camera unit takes a picture of the rear view and displays the picture on the screen of the display unit in close proximity to the driver. In this way, the image-pickup display apparatus can be utilized in place of the conventional side mirrors or the conventional rear-view mirrors.
In the image-pickup display apparatus serving as a portable video camera, on the other hand, the camera unit takes a picture of a photographic object and the screen of the display unit serves as a monitor of the photographic object.
In general, such an image-pickup display apparatus comprises a camera unit for taking a picture of a photographic object and a display unit for displaying the picture based on a picture signal output by the camera unit.
In the camera unit, a picture of a photographic-object image received through an image-pickup optical system is recognized by means of a solid image-pickup device such as a CCD (Charge Coupled Device) and the picture is converted into a picture signal by a signal processing circuit.
The display unit displays a photographed picture based on the picture signal output by the camera unit on a screen such as a liquid-crystal display panel.
By the way, the image-pickup display apparatus with such a configuration is designed so that the camera unit and the display unit independently carry out adjustments in accordance with the brightness of the circumference to produce an optimum picture.
To be more specific, a controller employed in the camera unit controls the image-pickup device and the signal processing circuit to adjust the diaphragm, changes the speed of the so-called shutter and/or adjusts the gain of a signal output by the CCD in accordance with the brightness of the circumference in order to correct the so-called exposure.
On the other hand, a driving controller employed in the display unit changes the contrast and the brightness of a picture appearing on the screen and/or adjusts the brightness of the back-light in accordance with the brightness of the circumference.
It is desirable, however, to carry out adjustments based on the brightness of the circumference so that a picture appearing on the screen of the display unit keeps up with variations in circumference brightness as quickly as possible. With the camera and display units carrying out the adjustments independently, nevertheless, the variation range of the level of a picture signal output by the camera unit increases while the so-called dynamic range of a display appearing on the liquid-crystal display panel of the display unit is narrow in some cases. The dynamic range is a range in which a taken picture can be represented. As a result, the level of the picture signal output by the camera unit goes beyond a dynamic range optimum for the display appearing on the liquid-crystal display panel of the display unit, raising a problem of generation of the so-called white or black collapse.
In addition, with the adjustment by the camera unit shifted along the time axis from the adjustment by the display unit, the level of the picture signal output by the camera unit may temporarily go beyond the dynamic range optimum for the display appearing on the liquid-crystal display panel of the display unit, making it difficult to keep up with variations in circumference brightness in a short period of time.
It is an object of the present invention addressing the problems described above to provide a picture-pickup display apparatus that is capable of producing an optimum screen display keeping up with variations in circumferential brightness by letting a camera unit and a display unit thereof carry out adjustments in a coordinated manner.
The object described above can be achieved by an image-pickup display apparatus provided by the invention which includes a camera unit comprising an image-pickup optical system, an image-pickup device having a light intercepting surface at a position of image formation by the image-pickup optical system, a signal processing circuit for generating a picture signal based on an image-pickup signal output by the image-pickup device, and a controller for correcting exposure by controlling the image-pickup device and the signal processing apparatus, and a display unit comprising a liquid-crystal display unit having a liquid-crystal display panel and a back-light, a driver for driving and controlling the liquid-crystal display panel, a back-light controller for driving and controlling the back-light, and a picture processor for outputting a driving signal to the driver on the basis of the picture signal generated by the signal processing circuit employed in the camera unit, wherein, receiving a drive/control signal output by the driver employed in the display unit as a feedback signal, the controller employed in the camera unit controls the image-pickup device and the signal processing circuit employed in the camera unit as well as the picture processor and the back-light controller employed in the display unit to put the drive/control signal in an optimum range.
According to the configuration, an image of a photographic object input through the image-pickup optical system and formed on the light intercepting surface of the image-pickup device is recognized by the image-pickup device generating an image-pickup signal which is converted by the signal processing unit into a picture signal. Then, the picture signal is supplied to the picture processor employed in the display unit outputting a driving signal to the driver to drive the liquid-crystal display panel. As a result, a picture appears on the liquid-crystal display panel.
By feeding back a drive/control signal output by the driver employed in the display unit to the controller in the camera unit, information on a picture appearing on the liquid-crystal display panel is supplied to the controller.
As described above, the controller corrects exposure by controlling the image-pickup device and the signal processing apparatus. In addition to the correction of exposure by controlling the image-pickup device and the signal processing circuit, the controller also controls the picture processor and the back-light controller employed in the display unit by referring to the information on the picture appearing on the liquid-crystal display panel so as to adjust the brightness and the contrast of the picture and the brightness of the back-light in order to put the drive/control signal in an optimum range or a dynamic range of the liquid-crystal display panel.
When the circumference is bright, for example, the image-pickup device employed in the camera unit is controlled by increasing the so-called shutter speed so as to lower the level of the picture signal. In this way, saturation of the image-pickup device can be avoided. In addition, the gain of the signal processing circuit is reduced. In the display unit, on the other hand, the brightness and the contrast of the display and the brightness of the back-light are increased so as to make the picture appearing on the liquid-crystal display panel bright.
When the circumference is dark, on the contrary, the image-pickup device employed in the camera unit is controlled by decreasing the so-called shutter speed so as to raise the level of the picture signal. In addition, the gain of the signal processing circuit is increased. In the display unit, on the other hand, the brightness and the contrast of the display are suppressed and the brightness of the back-light is decreased so as to make the picture appearing on the liquid-crystal display panel dark to reflect the circumference.
In another embodiment the camera unit further has a diaphragm device which is used for adjusting the quantity of light hitting the light intercepting surface after passing through the image-pickup optical system, and controlled by the controller along with the image-pickup device and the signal processing circuit in order to put the drive/control signal output by the driver employed in the display unit in an optimum range. The control of the diaphragm itself changes the quantity of light hitting the light intercepting surface after passing through the image-pickup optical system, allowing the controller to correct exposure with ease and with a high degree of reliability over a broad range.
In another embodiment the camera unit and the display unit are provided separately from each other; the camera unit has an output sub-unit for receiving a picture signal from the signal processing circuit; and the display unit has an input sub-unit for inputting a signal output by the output sub-unit employed in the camera unit.
In another embodiment the output sub-unit converts the picture signal into an analog signal and outputs the analog signal; the input sub-unit converts the analog signal received from the output sub-unit into a digital signal. Since the picture signal is transmitted by the camera unit to the display unit as an analog signal as described above, the picture signal can be transmitted with ease.
In another embodiment the output sub-unit transmits the picture signal by modulating a carrier signal, and the input sub-signal demodulates a signal received from the output sub-unit to extract the picture signal. Since the picture signal is transmitted by the camera unit to the display unit by modulation of a carrier signal, the picture signal can be transmitted with a higher degree of reliability by being hardly affected by external noise.
In another embodiment, the camera unit and the display unit are integrated to form a single body to allow a picture signal to be transferred from the signal processing circuit employed in the camera unit to the picture processor employed in the display unit directly. As a result, the circuit configuration can be made simple and the cost can be reduced.